Windows 7 - Mouse problem cursor moves way beyond right edge of screen

I recently noticed a problem with my cursor. When I move the mouse so that the cursor goes to the right edge of my screen, it doesn't stop at the right edge like it does when I move it to the left edge. The cursor will move far beyond the right edge and then I have to move the mouse the same "distance" for the cursor to re-appear on the right edge of my screen. When I first noticed this, I thought my mouse driver was dropping out on me. I'm using a Microsoft Intellimouse Optical that I bought new a couple months ago.

So my cursor will go to the left side of the screen and stop, just as it normally would. When I move the cursor to the right side of the screen, it will go beyond the right edge, sometimes FAR beyond the right edge and I have to move it the same distance to the left for the cursor to show up at the right hand edge of my screen. It not only does this on my desktop, but any program I'm using as well. I have tried re-installing the latest version of the mouse driver from microsoft but still have the same problem. Any suggestions? Thank you!

The system was set up for having 2 monitors for some reason. When I changed it back to a single monitor only, the problem went away.